The common thread is that most of the presenters & audience know at least one dialect of Lisp (e.g. Common Lisp, Scheme, Clojure, Emacs Lisp, etc). But it is definitely a polyglot (not just Lisp-related) group, and presentations on non Lisp-related subjects are encouraged.

The format is usually "educational lightning talks" (background + five-minute presentation + five minutes for Q&A), with all attendees invited to present if they feel like it. Followed by snacks.